The heart is an organ that pumps blood. The valves that make the blood flow in a fixed direction without backflow are essential for heart function. There are 4 chambers (2 atria and 2 ventricles) and these chambers are connected to 4 blood vessels (aorta, vena cava, pulmonary artery, and pulmonary vein).
The valve between the left atrium and the left ventricle is called the mitral valve; the valve between the right atrium and the right ventricle is called the aortic valve; and the valve between the right atrium and the pulmonary artery is called the pulmonary valve.
The valves should open and close completely as the heart beats. Backflow of blood or flow disturbance occurs when the valve does not move smoothly, including incomplete closing or opening. Heart valve disease is classified as blood leakage because of the incomplete closure of the valve (regurgitation) or incomplete opening of the valve (stenosis).
Mitral regurgitation is a disease causing heart failure. The heart becomes strained from the backflow of blood caused by incomplete closure of the mitral valve between the left atrium and left ventricle.
The standard treatment for mitral stenosis is the repair of the mitral valve by incising the heart after opening the sternum, or replacing the valve with an artificial valve. This treatment is very effective, but it is very invasive with a mortality rate of up to 5%. Because of this mortality rate, treatment is usually confined to severe mitral stenosis. However, a newer treatment with percutaneous mitral valvuloplasty, in which the mitral valve is repaired through a simple procedure by means of a catheter, prevents the need for surgery that includes incising the heart after opening the chest.
In line with this newer treatment, the detailed description of mitral cerclage coronary sinus annuloplasty was published in an international journal (Kim et al., Mitral cerclage annuloplasty, a novel transcatheter treatment for secondary mitral valve regurgitation: initial results in swine. Journal of American College Cardiology 2009; 754(7):638-51) and described in an international patent application (WO2008/060553), which application is herein incorporated by reference in its entirety. The usefulness of this technique is attributed to the circular pressure that can be applied to the perimeter of the mitral annulus.
The technique for percutaneous mitral valvuloplasty is as follows. The right ventricle is accessed through the jugular vein, and the cerclage thread is passed though the proximal septal vein by positioning the catheter in the coronary sinus. The thread can then be fed through the right ventricular outflow tract (RVOT), into the right ventricle, and then into the tissue adjacent to the mitral annulus. The mitral annulus is constricted when tension is applied to the thread: incomplete closure is reduced by making the two valve leaflets come into closer contact. Constricting the mitral annulus reduces the backflow of blood through the mitral valve.
Routing of the thread is achieved with a guide wire to position the cerclage thread around the mitral annulus. After a sheath is passed along the guide wire, the cerclage thread is inserted into the sheath and the sheath is removed.
However, it is difficult to pass the cerclage thread through the curved sheath as the cerclage thread is not as rigid as the guide wire. This problem extends surgical time and can result in an unfavorable outcome for the patient.
In addition, the adjacent cardiac tissue is often damaged during constriction of the mitral annulus by the relatively rigid cerclage thread.
Patent literature 1) WO 2008/060553 (THE GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY OF THE DEPARTMENT OF HEALTH AND HUMAN SERVICES) May 22, 2008.
Patent literature 2) KR 1116867 (Joon Hong Kim) Feb. 8, 2012.
Non-Patent literature 1) Kim et al., Mitral cerclage annuloplasty, a novel transcatheter treatment for secondary mitral valve regurgitation: initial results in swine. Journal of American College Cardiology 2009; 54(7):638-51.